Answer by Ken Miyamoto, produced screenwriter, former Sony Pictures script reader and story analyst, blogger:

Let’s start off with what are not some of the hallmarks. First, the notion that the more gore the better. Gore and shock value do not equal great horror or psychological thriller. Second, lots of computer graphis. If there is anything that is plaguing horror movies this century, it’s the overuse of CG. Computer graphics aren’t scary, plain and simple. CG backdrops and sets aren’t scary.

Now that we have that off of our chests, let’s delve into what makes a great horror and psychological thriller.

The Unknown. It’s what you don’t see that scares you the most because when you go home after watching the movie in the theater, your imagination plays with you, as it does when you’re in the theater watching a great horror movie or psy-thriller. You’re always watching and waiting for what’s around the corner, what’s in the shadows, etc. That’s what screenwriters and directors in those genres need to remember. It’s not about seeing overly conceptualized ghosts, vampires, zombies, or killers. It’s about knowing they’re there, somewhere, but not knowing when they’ll strike or where they’ll come from.

Imagery. Now, imagery isn’t about great CG or gore, as mentioned before. Imagery is about using the formerly mentioned unknown and then shocking us with images that won’t leave our head as we’re driving home. And such imagery can’t look like good CG. To me, filmmakers don’t want their audience to say, “That was some great CG,” because that means they knew it was CG. But regardless, some great imagery matters. And sometimes that’s just seeing something very briefly or half hidden. Sometimes it means something so shocking full front. But it has to be something that looks and feels real.

Fear. The best horror and psy-thrillers play with the fear that audiences have: spiders, needles, being chased, clowns, ghosts in the night, stalkers, the dark, etc. Whether the films are centered around such fears, or whether they have scene or sequences featuring them, fear is what thrills audiences. It’s why rollercoasters are so popular. It’s why horror movies and psy-thrillers are so popular.

The world. This could also be called the location in some cases: a haunted hotel (The Shining), a space station (2001), a haunted suburban house (Poltergeist), and so on. Such places are thrilling and horrific.

Those are just a few of the hallmarks of great horror movies and psy-thrillers.